1. Field of the Invention
The present invention relates to compositions and methods for treating obesity. Specifically, the present invention provides methods for treating obesity using polysaccharides isolated from Hirsutella sinensis as well as methods to prepare the polysaccharides.
2. The Prior Art
Traditional Chinese medicine has a long history in Asian countries dating back several thousands of years. One class of traditional remedies commonly in use consists of medicinal mushrooms such as Antrodia cinnamomea, Agaricus blazei Murrill, Ganoderma lucidum, and Ophiocordyceps sinensis, which contain a wide range of immuno-modulatory and bioactive compounds. The medicinal mushroom Ophiocordyceps sinensis has been used for centuries to promote health and longevity. Recent work has identified that the anamorphic, mycelium form of O. sinensis fruiting bodies is Hirsutella sinensis. Previous studies have shown that extracts of O. sinensis fruiting bodies and H. sinensis mycelium produce similar beneficial effects on laboratory animals, including anti-fatigue, anti-inflammatory, kidney-protecting, and libido-enhancing effects. However, the possibility that H. sinensis mycelium may produce anti-obesity effects has not been explored.
Obesity is now considered a disease condition associated with numerous health problems and a reduced life expectancy. Growing evidence indicates that obesity is closely linked with chronic, low-grade inflammation which can lead to insulin resistance, type 2 diabetes, fatty liver disease, cardiovascular disease, obstructive sleep apnea, and cancer. The high prevalence of obesity represents a major threat to public health, with an estimated 500 million obese people and 1.4 billion overweight individuals worldwide. Prevention of obesity is therefore a major challenge for modern societies.
Several treatments have been used to prevent and treat obesity in the general population, including calorie restriction, low-carbohydrate diets, and regular exercise. However, these treatments are difficult to implement over a long period of time and they are associated with low patient compliance. A number of treatments, including antibiotics and prebiotics, are being evaluated for the management of obesity and its related metabolic disorders. For example, antibiotic treatment alters the gut microbiota, reduces blood endotoxemia, and improves glucose tolerance in obese mice lacking the leptin gene (ob/ob mice) or in mice fed with a high-fat diet (HFD). In addition, prebiotics represent non-digestible, fermentable polysaccharides and oligosaccharides, which reduce body weight and exert anti-inflammatory effects, mainly by enhancing the growth of specific beneficial bacteria found in the gut. Prebiotics not only alter the intestinal microbiota but also maintain intestinal tight junction integrity and decrease blood endotoxemia caused by bacterial lipopolysaccharides (LPS). Modern diets tend to incorporate high levels of refined sugars and processed foods and are low in vegetables and prebiotics which would normally help maintain body weight and general health. Therefore, there is a need for safe and easy-to-use sources of prebiotics.
In view of the growing incidence of obesity in the human population and the difficulties observed in prevention and treatment, there is a need for alternative modes of prevention, treatment and control of this condition. New measures that can be introduced in the diet without necessitating considerable changes in lifestyle and without incurring in toxicity or adverse effects are particularly needed.